?? Operator for multiple-optionals - Overloads that extends the default ?? operator behaviour up to triple optionals

MultilevelOptionalCoalescing.swift

//
//  Created by Dorian Grolaux on 14/01/2020.
//  Copyright © 2020 Skwiggs Inc. All rights reserved.
//

import Foundation

/**
 Nil coalesces 2-level optionals in a single step
 */
func ??<T> (optional: T??, defaultValue: @autoclosure () throws -> T) rethrows -> T {
    return try optional as? T ?? defaultValue()
}

/**
 Nil coalesces 2-level optionals in a single step
 */
func ??<T> (optional: T??, defaultValue: @autoclosure () throws -> T?) rethrows -> T? {
    return try optional as? T ?? defaultValue()
}


/**
Nil coalesces 3-level optionals in a single step
*/
func ??<T> (optional: T???, defaultValue: @autoclosure () throws -> T) rethrows -> T {
    return try optional as? T ?? defaultValue()
}

/**
Nil coalesces 3-level optionals in a single step
*/
func ??<T> (optional: T???, defaultValue: @autoclosure () throws -> T?) rethrows -> T? {
    return try optional as? T ?? defaultValue()
}

Examples

Double optional

Now

let a: Int?? = 8
let b = a ?? 10

Before

let a: Int?? = 8
let b = a as? Int ?? 10

Triple optionals

Now

let a: Int??? = 4
let b = a ?? 9

Before

let a: Int??? = 8
let b = (a as? Int?) as? Int ?? 10